Method for forming articles at an elevated temperature

ABSTRACT

A method for hot/warm forming an article that includes heating a billet in a first heater; forging the heated billet in a forging die to form an intermediate workpiece; removing the intermediate workpiece from the forging die while a temperature of the intermediate workpiece is greater than or equal to a predetermined elevated temperature of 1,000 degrees F; and heat treating the intermediate workpiece before the intermediate workpiece has cooled below the predetermined elevated temperature.

The present invention generally relates to a method for forming articles, such as hubs, races, shafts and gear blanks, at an elevated temperature.

Conventional hot and warm forming processes for forming articles include hot/warm forging billets into an intermediate workpiece, processing batches of the intermediate workpieces through heat treating and tempering operations and the subsequent machining of the hardened and tempered intermediate workpieces to form a finished workpiece. These processes typically perform heat treating and tempering operations after the intermediate workpieces have cooled from a forging temperature to an ambient air temperature. While this process is satisfactory for the production of finished workpieces, there remains a need in the art for a more cost-effective method for hot/warm forming and heat treating of articles.

SUMMARY

This section provides a general summary of some aspects of the present disclosure and is not a comprehensive listing or detailing of either the full scope of the disclosure or all of the features described therein.

In one form, the present teachings provide a method for hot/warm forming an article. The method includes forming a billet from a length of stock; heating the billet in a first heater in an initial heating step to a heated billet temperature that is greater than or equal to a predetermined forging temperature; placing the heated billet into a forging die; operating the forging die to hot/warm forge an intermediate workpiece; removing the intermediate workpiece from the forging die; placing the intermediate workpiece in a second heater when the intermediate workpiece has an intermediate workpiece temperature that is greater than or equal to a predetermined elevated temperature of 1,000 degrees F., the intermediate workpiece not receiving energy to raise the intermediate workpiece temperature between the forging die and the second heater; heating the intermediate workpiece in the second heater to raise the intermediate workpiece temperature from the elevated temperature to a heat treating temperature; and quenching the intermediate workpiece after it is heated to the heat treating temperature in a quenchant to form a hardened intermediate workpiece.

In another form, the present teachings provide a method for hot/warm forming an article. The method includes heating a billet in a first heater; hot/warm forging the heated billet in a forging die to form an intermediate workpiece; removing the intermediate workpiece from the forging die while a temperature of the intermediate workpiece is greater than a predetermined elevated temperature of 1,000 degrees F.; and heat treating the intermediate workpiece before the intermediate workpiece has cooled below the predetermined elevated temperature.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application and/or uses in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. The drawings are illustrative of selected teachings of the present disclosure and do not illustrate all possible implementations. Similar or identical elements are given consistent identifying numerals throughout the various figures.

FIG. 1 is a schematic illustration of a forging operation for forming an article in accordance with the teachings of the present disclosure; and

FIG. 2 is a schematic illustration in flow chart form illustrating a method for hot/warm forming articles in accordance with the teachings of the present disclosure.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

With reference to FIG. 1 of the drawings, a forging operation 100 is schematically illustrated. The forging operation 100 is configured to convert stock 110 into a hardened intermediate workpiece 116, which can be processed through one or more manufacturing steps to form a finished workpiece 118. In the particular example provided, the hardened intermediate workpiece 116 can be suitably tempered and machined to form a torque converter hub, but those of skill in the art will appreciate that the present disclosure has application to other types of finished workpieces.

A length of stock 110 of an appropriate material, such as steel, can be cut at a saw 120 or other cutting device (e.g., shear press) to form a plurality of billets 112. The billets 112 can be processed through a first heater 130, such as an induction heater, to heat the billets 112 to an elevated forging temperature. The elevated forging temperature can be based on the material from which the billet 112 is formed, the amount of material that is to be moved during forging, etc. and in the particular example provided ranges between 1,900° F. to 2,000° F. The heated billets 112 can be processed through one or more forging dies 140 to forge the heated billets 112 into intermediate workpieces 114. The intermediate workpieces 114 that exit from the forging die 140 have cooled somewhat from their forging temperature but are typically at a temperature that is much higher than ambient air temperature. The intermediate workpieces 114 can be sequentially transmitted to a second heater 150, such as an induction heater, and heated to a hardening temperature. It will be appreciated that the heating of the intermediate workpieces 114 can be controlled in a desired manner to achieve a desired level and uniformity of heating. As such, it will be understood that the intermediate workpieces 114 have been heated to a desired level and with a desired uniformity when they have been heated to the hardening temperature. The heated intermediate workpieces 114 can exit the second heater 150 and thereafter plunged into a quenchant 160, such as oil or water, to cool the heated intermediate workpiece 114 so as to create a hardened intermediate workpiece 116 with a desired metallurgical microstructure. The hardened intermediate workpieces 116 can be collected from the quenchant 160 and processed through a tempering process in a desired manner, such as in batches. In the particular example provided, the hardened intermediate workpieces 116 are permitted to substantially cool (e.g., to ambient air temperature) and thereafter are heated in a third heater 180, such as a gas-fired heater, to heat the batch of hardened intermediate workpieces 116 to a tempering temperature. The third heater 180 can be employed to control the temperature of the hardened intermediate workpieces 116 in a desired manner, such as maintaining the hardened intermediate workpieces 116 at any desired tempering temperature for a desired length of time, to temper the hardened intermediate workpieces 116 in a desired manner. The hardened and tempered intermediate workpieces 116 can be processed through various machining processes 190, such as one or more chip-forming processes (e.g., milling, turning, grinding, drilling) or chip-less processes (e.g., shearing) to form a finished workpiece 118.

Preferably, the intermediate workpieces 114 have not substantially cooled before they are introduced to the second heater 150. The intermediate workpieces 114 may have substantially cooled if they reach a temperature lower than a predetermined elevated temperature. In one aspect of the present disclosure, if the temperature of the intermediate workpieces 114 decreases more than 45% of the hot/warm forging temperature it may be substantially cooled and sent to the reworking bin. In the particular example provided, if the intermediate workpieces 114 cool from the hot/warm forging temperature of 1,900° F. to 2,000° F. to below the predetermined elevated temperature of 1,000° F. they will be deemed to have substantially cooled such that the intermediate workpieces 114 will not be sent to the second heater 150. It will be appreciated that an optical pyrometer or any other temperature measuring device can be employed to measure the temperature of the intermediate workpieces 114.

With additional reference to FIG. 2 of the drawings, a flow chart schematically illustrates certain aspects of the methods of the present disclosure. At block 200, a length of stock 110 is introduced, for example steel. At block 210, a billet 112 may be severed from the length of stock 110. At block 230, the billet 112 may be introduced to a first heater 130 to raise the temperature of the billet 112 to a desired forging temperature. At block 240 the heated billet 112 can be placed into a forging die 140 and the forging die 140 can be operated to form an intermediate workpiece 114. At block 242 the forged intermediate workpiece 114 can be removed from the forging die 140. At decision block 244 the temperature of the intermediate workpiece 114 is determined. In the particular example provided, an optical pyrometer is employed, but those of skill in the art will appreciate that other temperature sensing devices could be employed in the alternative. If the temperature of the intermediate workpiece 114 is below a predetermined elevated temperature, the intermediate workpiece 114 is deposited in a rework station at block 246 and the methodology ends. Returning to decision block 244, if the temperature of the intermediate workpiece 114 is not below the predetermined elevated temperature, the intermediate workpiece 114 is placed into a second heater 150 at block 250 and heated to a hardening temperature. By processing the intermediate workpiece 114 through the second heater 150 immediately after forging, the residual heat in the intermediate workpiece 114 may be conserved so that less energy is required to heat the intermediate workpiece 114 to the hardening temperature.

The second heater 150 may generate heat by electromagnetic induction or any other suitable method of heat treatment to harden the intermediate workpiece. A temperature sensor, such as an optical pyrometer, can be employed by the second heater 150 at block 250 to control the second heater 150 in a manner such that the intermediate workpiece 114 is uniformly heated to the hardening temperature, for example, 1,800° F.

At block 260 the heated intermediate workpiece 114 may be removed from the second heater 150 and quenched in a quench bath of a suitable quenchant 160, such as oil or water, to form a hardened intermediate workpiece 116. The quench bath may have a plurality of heating control elements (not shown),which can include heaters and heat exchangers, to maintain a temperature of the quenchant 160 within a predetermined quenchant temperature range and/or an agitator to agitate the quenchant 160 to further improve quenching. At block 262, the hardened intermediate workpiece 116 may be removed from the quench bath by any suitable means, such as a conveyor (not shown). Excess quenchant 160 may be allowed to drip or be removed from the hardened intermediate workpiece 116 and flow back into the quench bath during conveyor travel. The conveyor may direct the hardened intermediate workpiece 116 into a bin (not shown) capable of holding a plurality of hardened intermediate workpieces 116.

At block 270, the hardened intermediate workpiece 116 may be cleaned. For example, the hardened intermediate workpiece 116 may be washed to remove residual quenchant 160. At block 280 the hardened intermediate workpiece 116 may be heated in a third heater 180 to temper the hardened intermediate workpiece 116. At block 290 the hardened and tempered intermediate workpieces 116 are machined to form a finished workpiece 118.

It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein, even if not specifically shown or described, so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims. 

1. A method comprising: forming a billet from a length of stock; heating the billet in a first heater in an initial heating step to a heated billet temperature that is greater than or equal to a predetermined forging temperature; placing the heated billet into a forging die; operating the forging die to forge an intermediate workpiece; removing the intermediate workpiece from the forging die; placing the intermediate workpiece in a second heater when the intermediate workpiece has an intermediate workpiece temperature that is greater than or equal to a predetermined elevated temperature of 1,000 degrees F., the intermediate workpiece not receiving energy to raise the intermediate workpiece temperature between the forging die and the second heater; heating the intermediate workpiece in the second heater to raise the intermediate workpiece temperature from the elevated temperature to a heat treating temperature; and quenching the intermediate workpiece after it is heated to the heat treating temperature in a quenchant to form a hardened intermediate workpiece.
 2. The method of claim 1, wherein the quenchant is an oil.
 3. The method of claim 1, wherein the quenchant is agitated when the intermediate workpiece is quenched.
 4. The method of claim 1, wherein the quenchant maintained at a quenching temperature within a predetermined range.
 5. The method of claim 1, further comprising tempering the hardened intermediate workpiece to form a tempered intermediate workpiece.
 6. The method of claim 5, further comprising machining the tempered intermediate workpiece to form a finished workpiece.
 7. The method of claim 5, wherein a plurality of the intermediate workpieces are tempered simultaneously in a single batch.
 8. The method of claim 5, wherein prior to tempering the intermediate workpiece the method includes washing the intermediate workpiece.
 9. The method of claim 1, further comprising monitoring the temperature of the intermediate workpiece when the intermediate workpiece is heated in the second heater.
 10. The method of claim 9, wherein monitoring the temperature of the intermediate workpiece comprises sensing the temperature of the intermediate workpiece with an optical pyrometer.
 11. The method of claim 1, wherein after the intermediate workpiece is removed from the forging die the method further comprises: gauging the intermediate workpiece temperature before the intermediate workpiece is placed in the second heater; and processing the intermediate workpiece in an alternative heat treating operation if the intermediate workpiece temperature is not greater than the predetermined elevated temperature.
 12. The method of claim 11, wherein gauging the intermediate workpiece temperature comprises sensing the intermediate workpiece temperature with an optical pyrometer.
 13. The method of claim 12, wherein the second heater is an induction heater.
 14. A method comprising: heating a billet in a first heater; forging the heated billet in a forging die to form an intermediate workpiece; removing the intermediate workpiece from the forging die while a temperature of the intermediate workpiece is greater than or equal to a predetermined elevated temperature of 1,000 degrees F.; and heat treating the intermediate workpiece before the intermediate workpiece has cooled below the predetermined elevated temperature.
 15. The method of claim 14, wherein heat treating the intermediate workpiece comprises heating the intermediate workpiece in a second heater to elevate the temperature of the intermediate workpiece to a predetermined heat treating temperature and thereafter quenching the intermediate workpiece in a quenchant to form a hardened intermediate workpiece.
 16. The method of claim 15, further comprising tempering the hardened intermediate workpiece.
 17. The method of claim 16, further comprising machining the tempered intermediate workpiece to form a finished workpiece.
 18. The method of claim 16, wherein a plurality of the intermediate workpieces are tempered simultaneously in a single batch. 